Polymer supported metal thin films for flexible and stretchable applications need to have exceptional electro-mechanical behavior. Typically, brittle metal films thicker than 300 nm will fail at low strains. It will be demonstrated that with residual stress and microstructural tuning, a 500 nm thick Mo film on polyimide has a high crack onset strain and does not fail electrically after 1000 tensile straining cycles of 1% due to a novel zig–zag microstructure. The zig–zag microstructure imparts a crack deflecting behavior which ensures longer lifetimes. As a consequence, a high crack onset strain does not indicate better behavior under cyclic loading conditions.